Process and apparatus for wet spinning slub yarn



July 3, 1962 R. wcooau. 3,042,432

PRUCESS AND APPARATUS FOR WET SPINNING SLUB YARN Original Filed April 50, 1958 2 Sheets-Sheet 1 INVENTOR RUDOLPH WOODELL A ORNEY July 3, 1962 R. WOODELL 3,042,432

PROCESS AND APPARATUS FOR WET SPINNING SLUB YARN Original Filed April 50, 1958 2 Sheets-Sheet 2 Big-4 IN VENTOR RUDOLPH WOODELL ATTORNEY United States Patent Ofifice 3,042,482 Patented July 3, 1962 7 Claims. c1. 18--54) This invention relates to a process and an apparatus for preparing a novel slub yarn composed of continuous filaments. More particularly it relates to preparing the novel yarn by a Wet-spinning process.

Slub yarns are well known and are characterized by numerous bunches, protrusions or other similar variations in cross section along the length of the Yarn. The variations or slubs may be spaced at equal or unequal distances along the length of the yarn and the slubs may vary in width and length depending on the method of manufacture. When made into fabrics, such yarns provide the decorative efiect of slubs distributed throughout the surface of the fabric.

Producing slub yarns from natural fibers is a tedious and expensive operation. With the exception of silk, the natural'fibers of animal, vegetable and mineral origin exist in only relatively short lengths. To produce constant denier yarn from such staple fibers requires a complex series of operations to align the fibers, combine them into an elongated bundle called roving and draw the roving to a smaller diameter on a spinning frame or twisting frame while twisting to prevent excessive slipping of adjacent fibers past each other. To produce slubs on the yarn, a regular or irregular variation may be introduced in the speed at which the roving is delivered to the twisting roller. The resulting slub yarn, although providing bulky protrusions for desirable decorative effects in fabrics, has the undesirable characteristics of constant denier staple yarn. The yarn has loose ends, is fuzzy, and pills.

Artificial fibers areproduced most easily as continuous filaments by an extrusion process. Forming yarn by combining a plurality of continuous filaments is much easier than the staple process previously described. Forming slub yarn directly from continuous filaments, although also relatively easy, is not completely satisfactory. The slub yarn may be produced by depositing small predetermined accretions of filament-forming material on an extruded base thread of continuous filaments. Another method involves using an extrusion pump controlled to produce a surging action during extrusion. Still another method involves drawing the filaments at regularly or irregularly varying linear speeds to impart stretch to the filaments which make up the yarn. In all these methods the resulting continuous filament yarn may be more properly described as a thick and thin yarn or a yarn of variable denier rather than a slub yarn. The resulting yarn shows gradual changes from thick to thin to thick, etc., rather than the bulky protrusions of slubs on staple yarn. In a wet-spinning process, the effect of the coagulating liquid on the yarn flowing through it is to reduce the variation in denier still further.

Certain slub yarns have been produced by the wet-spinning method by causing the filaments, while in a partially coagulated state, to pile up and then become thickened and stuck together at intervals. Such slubs, however, are hard, lumpy protrusions which do not lend themselves well to the production of fabrics of outstanding aesthetic appeal.

It is an object of this invention to produce a slub yarn from continuous filaments resembling the slub yarn from staple fibers in the desirable bulky protrusions or bunches distributed at intervals along the length of the yarn, yet

retaining the characteristic freedom from loose ends, fuzziness and pilling of continuous filament yarn. Another object is to provide a process for preparing continuous filament slub yarn, more particularly a wetspinning process for preparing regenerated cellulose continuous filament slub yarn. A further object is a novel apparatus for preparing the yarn by a wet-spinning process. Other objects will appear hereinafter.

These objects are accomplished by the present invention which provides a yarn comprising a plurality of continuous filaments individually looped upon themselves at intervals along their lengths and characterized by the presence of ring-like loops or slubs that are spaced at random intervals along the length of the yarn. Each of the filaments may be of variable or constant denier. The loops are formed by the filaments doubling back upon themselves, crossing and then proceeding in substantially the original direction. In mathematics, a curve of this type is said to have a crunode. Hence the filaments may be said to display crunodal loops at intervals along their length. In other words, the slubs in the yarn are composed of individual filaments having the same (or variable) denier and crunodal loops. The intervals between slubs will be at least 0.5 inch and may range from 4 to 20 inches or more. The length of the slubs may range from inch to 4 inches. The contrast between slubs and the base yarn must be substantial to provide desirable effects in the ultimate fabric. The denier of the slubs must be more than 2.5 times, preferably 4 to 10 times the denier of the base yarn. The slubs are characteristically tight and are not readily pulled apart, although the individual filaments do not adhere to each other.

The process for producing this yarn comprises extruding a filament-forming solution through spinneret orifices into a coagulating liquid to form filaments of either variable or constant denier, passing the filaments into a tube (or conduit), forcing coagulating liquid through the tube to transport the filaments through the tube and coagulate the filaments sufficiently that they do not stick together, discharging the filaments from the tube against a baffle disposed in the path of the filaments, drawing the filaments from the baffle at a rate less than the rate of discharge of the filaments from the tube to form loops and converging said looped filaments into a slub yarn.

In another embodiment, blended yarns may be prepared by feeding a finished yarn into the tube entrance along with the freshly extruded yarn. In this manner the finished yarn becomes intermingled with the filaments of the freshly extruded yarn to form a composite yarn of the desired type.

Since the rate of discharge of the filaments from the tube and the rate of Withdrawal of the filaments from the baffie cannot be measured directly, it is necessary to resort to the following method to insure that the relationship between these rates, as expressed in the statement of the invention, is obtained. The rates that can be measured are the linear velocity of the bath which carries the filaments through the tube and the peripheral speed of the feed Wheel which serves to draw the filaments from the baifie. It has been discovered that if these two speeds, bath velocity and feed wheel speed, are first adjusted so that the filaments do not strike the baffie but travel directly to the converging means, and then the ratio of feed Wheel speed to linear bath velocity is reduced by 15 to 50%, the desired relationship is obtained and satisfactory slub formation results. This ratio may be reduced by reducing the feed Wheel speed 15 to 50% or increasing the bath velocity by 18 to The exact reduction of this ratio between 15 and 50% for optimum slub formation will depend on the yarn denier, spinning speed, bath composition, desired slub frequency,

and desired contrast between slub and base denier. The ultimate ratio of feed wheel speed to bath velocity, has generally been found to be between 0.50 and 1.30.

The apparatus for producing the yarn comprises a spinneret, means for supplying a filament-forming solution to the spinneret, a container for immersing the spinneret in coagulating liquid, a conduit through which the filaments pass after extrusion from the spinneret, means for forcing liquid to pass through the conduit along with the filaments, a baffle disposed in spaced relation with the spinneret and the conduit and in the path of the filaments to cause the filaments to impinge thereon, a container for coagulating liquid so disposed that the bafile and at least one end of the conduit may be immersed in the liquid, means for withdrawing the filaments from the baffle at a rate less than the rate of feed of filaments against the baflie, and means for converging the filaments into a yarn.

FIGURE 1 is an illustration of one of the yarns of this invention.

FIGURE 2 is an illustration of another yarn of this invention.

FIGURE 3 is a view in perspective of one arrangement for producing the yarn.

FIGURE 4 is a view in perspective of another arrangement for producing the yarn.

FIGURE 5 illustrates a vertical tube arrangement for spinning the yarn.

In FIGURE 1, the slub yarn is composed of a plurality of constant denier filaments.

In FIGURE 2, the slub yarn is composed of a plurality of variable denier filaments.

In FIGURES 3 and 4, the spinning solution from the main supply pipe is led through pipe, 12, to a conventional gear type pump, 14. The pump, 14, meters the spinning solution through pipe, 16, to candle filter, 18, and into the spinneret, 20. When variable denier yarns are desired, a second pump, 22, intermittently forces additional spinning solution to the spinneret, 20. When constant denier filaments are desired, the second pump, 22, is omitted from the system. The spinning solution, as it emerges from the spinneret, is coagulated into filaments, 26, due to the coagulating effect of the coagulating liquid, 28, contained in tank, 34, and trough, 30. The extruded filaments proceed through the trumpetlike tube, 32, and impinge upon the plate, 36, immersed in the coagulating liquid, 28. Upon hitting the plate, 36, the completely coagulated filaments become entangled in a mass of loops, whorls, and coils. The entangled filaments are then led under convergence guide, 24, around draw-off roller, 38, snubber roller, 40, into a reciprocating funnel, 42, which guides it into a rotating bucket, 44, where the yarn is collected in the form of a cake.

In FIGURE 4, an additional spinneret, 46, is immersed in the coagulating liquid, 28, to form additional filaments, 48, which are combined with the entangled filaments at convergence guide, 24. This second yarn merely acts as a stress-bearing element for the slub yarn.

In FIGURE 5, the spinning solution is supplied to spinneret, 50, by means of a pipe, 52. Upon emergence from the spinneret, 50, the spinning solution is coagulated into filaments, 60, due to the action of the coagulating liquid, 56, contained in tank, 54. An overflow, 58, allows a constant head to be maintained in tank, 54. The filaments, 60, and coagulating liquid, 56, proceed through the tube, 62, and then impinge on a dish-shape slub bowl, 64, where they become entangled in a mass of loops, whorls, and coils. The slub bowl, 64, is immersed in the coagulating liquid, 66, contained in trough, 68. The resulting filaments, 70, are then converged at convergence guide, 72, led around roller, 74, draw-off roller, 76, and snubber roller, 78, and sent to windup. A second spinneret, 80, immersed in the bath, 66, may be used to form support filaments, 32. When support filaments, 82, are to be used, it is generally desirable to combine these filaments with the slub-yarn at convergence guide, 72.

The invention will be described with respect to regenerated cellulose filaments and yarns. However, the invention is not restricted thereto but is meant to include filaments and yarns produced from other filament-forming materials by wet-spinning processes such as cellulose nitrate, cellulose acetate, vinyl polymers, acrylic polymers, proteins, polyamides, and the like.

EXAMPLE I A standard viscose solution containing 7% recoverable cellulose and 6% alkali, calculated as sodium hydroxide, at a salt index of 4.6 and a viscosity of 40.5 poises is spun according to the spinning arrangement illustrated in FIG- URE 3 omitting, however, the second pump 22. The viscose spinning solution after passing through a filter, 18, is extruded through the spinneret, 20, into a coagulating and regenerating bath in tank, 34. The spinneret is /2 inch in diameter and contains 40 orifices of .0035 inch diameter each. The coagulating bath is at a temperature of 55 C. and contains 9.5% sulfuric acid, 19.25% sodium sulfate, 3.5% zinc sulfate and 2.0% glucose.

The extruded viscose filaments, 26, are introduced into a trumpet-like tube, 32, having an inside diameter of 7 millimeters and a length of 18 inches. The filaments are carried through the tube by the flowing bath liquid. The liquid is forced to flow through the tube at a linear rate of 52.8 yards per minute by enclosing a portion of the bath encompassing the spinneret and the tube entrance by tank, 34, and providing a bath head of about 4 inches.

Upon emergence from the tube the filaments, which are completely coagulated, strike the plate, 36, a 4 inch by 5 inch lead rectangle about 2 to 3 inches from the outlet of the tube, 32, perpendicular to the bottom of the spinning bath tank and turned about 5 to 10 in the direction of the windup. By splashing against the plate the filaments become entangled in a mass of loops, whorls and coils; However, since the filaments are completely coagulated, they do not adhere to one another. Adherence of filaments must be avoided to prevent the formation of harsh, brittle slubs resulting from stuck filaments.

The filaments are converged into a yarn at convergence guide, 24, a hook type guide fastened to the base of the bath tank, and led to the draw-off roller, 38, and snubber roller, 40. The draw-off roller is 6 inches in diameter and is driven at a peripheral speed of 45.3 yards per minute. The tension on the yarn between the convergence guide and the draw-off roller is maintained between 10 and 20 grams. After two passes around the roller, 38, and a single pass over the snubber roller, 40, the yarn is collected in the rotating bucket, 44. The yarn is then washed, dried and wound onto cones in the conventional manner of the viscose process.

In order to adjust the speed of the yarn as it is drawn away from plate, 36, to a lower speed than the speed of the thread emerging from the tube to conform to the aforementioned ratio, the following technique is employed. The feed wheel speed is first adjusted to a speed to carry the yarn almost to plate, 36, by the bath stream discharged from the tube, 32, but is then pulled from the stream toward the convergence hook guide, 24, without striking the plate. This condition is called the zero point since the thread is obviously being drawn away at substantially the same rate at which it is discharged from the tube. At this point, it is found that the peripheral speed of the feed wheel is 58.7 yards per minute. The feed wheel speed is then reduced 22.8% to a speed of 45.3 yards per minute where excellent slub formation is obtained. The difference in the feed wheel speed, 58.7 yards per minute, and the bath velocity, 52.8 yards per minute, at the zero point is due to a small amount of stretch which it has been found is advantageous to impart to the filaments.

The following tables show the conditions required to obtain excellent slub formation with yarns of various base deniers at various spinning speeds when spinning into the same bath and under the same general conditions as outlined above. For the extremely heavy denier yarn presented in Table 3, a tube having an inside diameter of 15 millimeters, instead of 7 millimeters, is used.

Table I 150 DENIER- lO FILAMENT YARN Bath Head, inches 4 7 12 18 Linear Bath Velocity, YJLIII 52.8 70. 3 97. 6 117.0 Feed Wheel Speed, zero point,

y.p.m 58.7 92.2 125.6 175.1 Feed Wheel Speed, Optimum Slub,

y.p.m 45.3 71.2 104.1 136.0 Reduction in Ratio of Feed Wheel Speed to Linear Bath Velocity,

to Bath Velocity 0.85 1.01 1.06 1.16

Table II 450 DEN1ER-120 FILAMENT YARN Bath Head, inches 4 7 12 18 Linear Bath Velocity, y.p.n1 49.6 68. 9 87.4 115. 5 Feed Wheel Speed, zero point,

y.p.m 62.9 86.4 120.1 185.7 Feed Wheel Speed, Optimum Slub,

y,p.rn 40. 6 57.6 89.0 143. 9 Reduction in Ratio of Feed Wheel Speed to Linear Bath Velocity, Percent 35. 4 33. 4 26. 22. 6 Optimum Ratio of Feed Wheel Speed to Bath Velocity 0.82 0. 83 1.02 1. 25

Table III 2200 DENIER-72O FILAMENT YARN Bath Head, inches 4 7 Linear Bath Velocity, y.p.n1 47. 4 64. 7 Feed Wheel Speed, zero point, y.p.m 57. 6 78. 6 Feed Wheel Speed, Optimum Slnb, y.p.rn. 39.3 57.6 Reduction in Ratio of Feed Wheel Speed to Linear Bath Velocity, Percent 31. 26. 7 Optimum Ratio of Feed Wheel Speed to Bath Velocity 0. 83 O. 89

The yarn as illustrated in FIGURE 1 is characterized by slubs spaced at random intervals along the length of a substantially smooth yarn. The loops, which make up the slubs, are intertwined in the yarn to the extent that they are not readily pulled apart. The denier of the slubs range from 4 to 7 times the denier of the base yarn.

The yarn is used as filling in the weaving of plain and twill weave fabrics. Undyed slub yarn is used in the plain fabric and produces a silk Dupioni or shantung effect. The dyed yarn is used in a twill weave fabric and the fabric displays a two-tone splash effect.

EXAMPLE II Viscose containing 6.25% recoverable cellulose and 5.75% alkali, calculated as sodium hydroxide, is prepared in the conventional manner and extruded at a salt index of 4.3 and a viscosity of 41 poises into the coagulating bath of Example I using the spinning arrangement illustrated in FIGURE 5 omitting, however, the second spinneret, 80. The extruded filaments are introduced into a tube having an inside diameter of inch and a length of '15 inches. The filaments are carried through the tube by the flowing bath liquid. The liquid is forced to flow through the tube at a rate of 2.3 gallons per minute by adjusting the level of bath in the tank, 55, surrounding the spinneret to give a total bath head of 17 inches. The lower end of the tube, 62, is immersed for a depth of one inch in the coagulating bath held in the trough, 68. After emerging from the tube, the filaments strike the bottom of the slub bowl, 64, which is located 2 /4 inches below the tube exit. The slub bowl is made of lead and has a diameter of 3 inches and an inside depth of2' /z inches. The yarn is drawn away from the slub bowl in a generally horizontal direction, passed for a distance of 10 /2 inches through the coagulating bath, 66, to a Y convergence guide (not shown), then for a further distance of 9 inches through the bath, under a hook guide, 72, around roller guide, 74, and up to and around a rotating draw-01f roller, 76, and snubber roller, 781, and finally downwardly into a centrifugal spinning bucket. The peripheral speed of the draw-off roller, which is power driven, is 74 y.p.m. In arriving at the conditions of bath flow and feed wheel speed indicated above, the feed wheel speed is first adjusted to the zero point as described in Example I and then the speed is reduced 30% to ob tain optimum slub formation.

The yarn is characterized by slubs spaced at random intervals along the length of the yarn. The loops which make up the slubs are intertwined in the yarn to the extent that they are not readily pulled apart. The denier of the slubs ranges from 3 to 6 times the denier of the base yarn. The distance between slubs varies considerably but is greater than 0.5 inch in all cases.

EXAMPLE III Viscose containing 7% recoverable cellulose and 6% alkali, calculated as sodium hydroxide, is prepared in the conventional manner. The viscose is extruded at a salt index of 4.2 and a viscosity of 39 poises into a spin ning bath containing 11% sulfuric acid, 19.75% sodium sufate, 0.7% zinc sulfate and 2% glucose, the temperature of the bath being 47 C. A spinning arrangement of the type shown in FIGURE 5 is used omitting, however, the second spinneret, The spinning tube diameter is 0.276 inch and the end of the tube is submerged to a depth of one inch in the spinning bath in the lower trough, 68. The slub bowl in 3 inches in diameter and has a depth of 1% inches and the bottom of the bowl is placed 1% inches below the end of the spinning tube, 62. The length of the tube and the bath head employed are shown in the table below. Zero twist poly(ethylene terephthalate) yarn is fed into the top of the spinning tube, 62, and thus combines with the freshly spun rayon filaments to form a composite slub yarn. Various combinations of poly(ethylene terephthalate) yarn and rayon are prepared in this manner as shown in the table below. After leaving the slub bowl, the composite yarn is carried for a distance of 10 inches through the bath, over a Y convergence guide, then for a further distance of 15 inches through the bath to a hook guide, 72, a roller guide, 74, and upwardly to a power-driven feed wheel rotating at a peripheral speed of yards per minute and then downwardly into a spinning bucket where it is wound into a cake in the conventional manner.

The yarn is characterized by slubs spaced at random intervals along the length of the yarn. The loops which make up the slubs are intertwined in the yarn to the ex tent that they are not readily pulled apart. The denier of the slub ranges from 3 to 6 times the denier of the base yarn. The distance between slubs is in excess of 0.5 inch. When the yarn is woven into a fabric, very attractive surface effects are obtained. In addition, the fabrics are superior in resilience and launderability as compared to 100% rayon fabrics.

BLENDED YARNS Rayon Poly (ethylene terephthalate) 'luhe Bath Length, Head,

in. in. Denier Fila- Denier Filaments merits EXAMILE 1v Viscose containing 7% recoverable cellulose and 6% alkali calculated as sodium hydroxide, is prepared from wood pulp in the conventional manner using 30% carbon disulfide based on the weight of the air-dried pulp. The solution is ripened to a salt index of 4.0 and spun according to the spinning arrangement illustrated in FIGURE 3. The viscose from the main supply pipe is led through pipe, 12, to a conventional gear-type pump, 14. The pump metered t-he viscose solution through pipe, 16, to candle filter, 18, and into the spinneret, 20. There is also a second pump, 22, to draw viscose solution from the main supply pipe and to pulse the solution to the spinneret intermittently.

The variable denier filaments, 26, are extruded from the spinneret, 20, into a coagulating and regenerating liquid, 28, contained in tank, 34, and trough, 30. The spinneret is /2 inch in diameter and contains 40 orifices, each of 0.0035 inch diameter. The bath is at a temperature of 50 C. and contains 10% sulfuric acid, 22% sodium sulfate, 0.7% zinc sulfate and 2.0% glucose. The extruded filaments are introduced into a trumpetlike tube, 32, having an inside diameter of 7 millimeters and a length of 30 inches. The filaments are carried through the tube by the flowing bath liquid. The liquid is forced to flow through the tube by enclosing the portion of the bath, encompassing the spineret and the tube entrance, by tank, 34, and providing a bath head of about 4 /2 inches.

Upon emergence from the tube the filaments, which are completely coagulated, strike the plate, 36, a 4 inch lead square, which is placed 2 to 4 inches from the outlet of the tube, perpendicular to the bottom of the spinning trough, 30, and turned about 5 to in the direction of the windup. By splashing against the plate the filaments become entangled in a mass of loops, whorls and coils. However, since the filaments are completely coagulated, they do not adhere to one another. Adherence of the variable denier filaments must be avoided to prevent the harsh, brittle slubs that usually result from stuck filaments. The speed of drawing the yarn from the plate is adjusted so that it is below the rate of discharge from the outlet of the tube.

The entangled filaments are pulled away from the plate and converged into a yarn at the convergence guide, 24, which may be of the hook type as shown and made of glass or other smooth, bath-resistant material. The filaments are then led at a speed of about 50 yards per minute to the draw-off roller, 38, which is a positively driven feed wheel. After several passes around the feed wheel and a snubber roller, 40, the yarn bundle is passed into a reciprocating funnel, 42, which guides it into a rotating bucket, 44, where the yarn is collected as a cake. The yarn is then washed, dried and wound onto cones in the conventional manner.

In order to adjust the speed of the yarn as it is drawn away from plate, 36, to a lower speed than the speed of the thread emerging from the tube to conform to the aforementioned ratio, the technique of Example I is employed. At the zero point the peripheral speed of the feed wheel is about 60 yards per minute. The feed wheel speed is then reduced about to a speed of about 48 yards per minute to obtain excellent slub forma tion. The difference in the feed wheel speed of 60 yards per minute and the bath velocity which may only be about 50 yards per minute at the zero point, is due to a small amount of stretch which it has been found advantageous to impart to the filaments.

'The resulting yarn, as illustrated in FIGURE 2, is characterized by bulky slubs spaced at random intervals along the length of the variable denier yarn. The loops which make up the slubs are intertwined in the yarn to the extent that they are not readily pulled apart. The denier of the slubs ranges from 4 to 7 times the average denier of the base yarn. The average denier of the base yarn may range from 60 to 900 denier or higher.

8 EXAMPLE V Viscose containing 6.25% recoverable cellulose and 5.75% alkali, calculated as sodium hydroxide, is prepared in the conventional manner and extruded at a salt index of 4.3 and a viscosity of 41 poises into the coagulating bath of Example IV using the spinning arrangement illustrated in FIGURE 5. The pump arrangement of Example IV is used to cause intermittent pulsations in the viscose stream and thus vary the denier of the yarn. The extruded filaments are introduced into a tube, 62, having an inside diameter of inch and a length of 15 inches. The filaments are carried through the tube by the flowing bath liquid. The liquid is forced to flow through the tube at a rate of 2.3 gallons per minute by adjusting the level of bath, 56, in the tank, 54, surrounding the spinneret, to give a total bath head of 17 /2 inches. The lower end of the tube, 62, is immersed for a depth of one inch in the coagulating bath, 66, held in the lower trough, 68. After emerging from the tube, the filaments strike the bottom of the slub bowl, 64, which is located 2% inches below the tube exit. The slub bowl is made of lead and has a diameter of 3 inches and inside depth of 2 /2 inches. The yarn is drawn away from the slub bowl in a generally horizontal direction, passed for a dis- H tance of 10 /2 inches through the coagulating bath, 66,

to a Y convergence guide, then for a further distance of 9 inches through the bath, under a hook guide, 72, and a roller guide, 74, up to and around a rotating draw-off roller, 76, and snubber roller, 78, and finally downwardly into a centrifugal spinning bucket. The peripheral speed of the draw-off roller, which is power driven, is 74 y.p.rn. In arriving at the conditions of bath flow and feed Wheel speed indicated above, the feed wheel speed is first adjusted to the Zero point as described in Example I and then the speed is reduced 30% to obtain optimum slub formation.

The yarn is characterized by slubs spaced at random intervals along the length of the yarn and by denier variations due to the thick and thin sections in the filaments arising from the variation in the extrusion of the viscose as described above. The loops which make up the slubs are intertwined in the yarn to the extent that they are not readily pulled apart. The denier of the slubs ranges from 3 to 6 times the average denier of the base yarn. The distance between slubs varies considerably but is greater than 0.5 inch in all cases.

EXAMPLE VI Viscose containing 7% recoverable cellulose and 6% alkali, calculated as sodium hydroxide, is prepared in the conventional manner. The viscose is extruded at a salt index of 4.2 and a viscosity of 39 poises into a spinning bath containing 11% sulfuric acid, 19.75% sodium sulfate, 0.7% zinc sulfate and 2% glucose, the temperature of the bath being 47 C. The pump arrangement of Example IV is employed to pulsate the viscose and cause denier variation in the yarn. A spinning arrangement of the type shown in FIGURE 5 is used. The spinning tube diameter is 0.276 inch and the end of the tube is submerged to a depth of one inch in the spinning bath in the lower trough, 68. The slub bowl is 3 inches in diameter and has a depth of 1% inches and the bottom of the bowl is placed 1% inches below the end of the spinning tube. The length of the tube and the bath head employed are shown in the table below. Zero twist poly(ethylene terephthalate) yarn is fed into the top of the spinning tube, 62, and thus combines with the freshly spun rayon filaments to form a composite slub yarn. Various combinations of poly(ethylene terephthalate) yarn and rayon are prepared in this manner as shown in the table below. After leaving the slub bowl, 64, the composite yarn is carried for a distance of 10 inches through the bath, over a Y convergence guide, then for a further distance of 15 inches through the bath to a hook guide, 72, and a roller guide, 74, upwardly to a power-driven draw-01f roller,

76, and snubber roller, 78 (rotating at peripheral speeds of 100 yards per minute) and then downwardly into a spinning bucket where it is Wound into a cake in the conventional manner.

The yarn is characterized by denier variations due to the pulsating viscose delivery and slubs spaced at random intervals along the length of the yarn. The loops which make up the slubs are intertwined in the yarn to the extent that they are not readily pulled apart. The denier of the slubs ranges from 3 to 6 times the average denier of the base yarn. The distance between slubs is in excess of 0.5 inch. When the yarn is woven into fabric, very attractive surface effects are obtained. In addition, the fabrics are superior in resilience and launderability as compared to 100% rayon fabrics.

If spinning conditions are such that excessive yarn breakdowns result, then the embodiment shown in FIG- URES 4 and 5 may be used advantageously. In this arrangement a second spinneret, 46 or 80, is used. The filaments from the second spinneret are extruded into the bath and passed directly to the convergence guide, 24, or 72, without impinging upon the baffie. This second yarn acts merely as a stress-bearing element for the slub yarn to prevent breaks.

The yarn can be produced by both horizontal and vertical tube spinning arrangements using the standard viscoses, baths and treatments of the viscose industry. The variation in denier, which is produced by the double pump system illustrated above, can also be produced using any of the methods known in the art for imparting a pulsating motion or surging action to the filament-forming solution prior to its passage through the spinneret. The spinning, draw-oh, or peripheral feed wheel speed (all interchangeable terms) may vary up to 100 yards per minute or higher. Critical additions to the standard process, besides the means for pulsating the filament-forming solution when forming variable denier filaments, are the spinning tube, the enclosure for forcing bath liquid through the tube and the baffle or slub bowl which may be a screen, plate, or curved surface of lead, glass, porcelain, plastic or the like.

It is generally preferable to operate with the tube exit below the surface of the bath, however, under certain conditions it may be practical and even desirable to have the tube exit above the bath. The baffle or slub bowl must, of course, be submerged in the bath.

The regulation of the speeds at the tube exit and at the draw-off device, in the manner previously discussed, is an important consideration for optimum results. Determination of the aforementioned zero point is best accomplished by adjusting the linear bath velocity and peripheral feed wheel speed to the same value, i.e., a 1:1 ratio. If at this point the yarn is observed to strike the plate, then the feed wheel speed is increased (or the bath velocity decreased) until the zero point (the point at which the yarn just misses the plate and travels directly to convergence guide) is reached. If, on the other hand, the yarn is pulled more or less directly from the tube exit to the convergence or hook guide, then the feed Wheel speed must be decreased (or the bath velocity increased) to reach the zero point.

It should also be noted that the ratio of the speed of the feed wheel to the linear bath velocity through the spinning tube is not necessarily 1:1 at the zero pointl due to differences in the amount that the yarn is stretched between the hook guide and the feed wheel under various spinning conditions, and to the possibility that under same conditions, the rate of bath flow through the tube may exceed the yarn speed. However, the ratio of feed wheel speed to bath flow, both expressed in yards per minute, will usually fall in the range of 0.50 to 1.30 whenthe system is adjusted to produce a satisfactory slub yarn. When the horizontal tube set-up is used the ratio will usually fall in the range of 0.75 to 1.30 while with the vertical tube arrangement, the ratio will usually fall in the range of 0.50 to 1.0.

In commercial operation, bath heads greater than about six inches may be difficult to obtain with horizontal spinning tube arrangements without cumbersome modifications of the existing equipment. Therefore, it is desirable that an eductor be fitted on the exit end of the spinning tube to add a pressure equivalent to an increase in the existing bath head. A typical eductor may comprise a length of heavy wall plastic tubing, abutting the exit end of the spinning tube and held in place by a suitable sleeve. At the end abutting the spinning tube the inside diameter of the eductor is the same as the spinning tube. From the opposite end of the eductor tube the opening: is counterbored to provide a slightly larger inside diameter. The counterbore may extend slightly over one-half the distance into the plastic tube. Additional bath liquid is introduced through small openings in the wall of the plastic tube. These openings are angled toward the exit end of the eductor tube. The additional liquid may be brought into the eductor tube in any suitable manner. One possibility is to bring the liquid in through another tube fitted through a cylindrical opening in the aforemen tioned sleeve. A slot cut around the surface of the eductor tube and from which the angled openings originate may conduct the bath liquid into the eductor tube. The eductor is particularly desirable when high spinning speeds are used, speeds of 75 y.p.m. or higher, and the necessary bath heads cannot be obtained by conventional means.

Alternately, the necessary pressure head may be sup plied in a horizontal spinning arrangement -by enclosing the spinneret and the spinning tube entrance in a pressure tight enclosure and providing a standpipe in the bath supply line to maintain the desired head.

Composite yarns comprising rayon filaments mingled with non-cellulosic filaments or with other cellulosic filaments may be prepared by introducing a finished yarn having the desired characteristics into the entrance to the spinning tube as described above. By this means the properties of the slub yarn may be modified over a wide range to suit the particular end use for which the yarn is intended. Among the yarns which may be suitably blended with the rayon filaments in this manner are polyester yarns, polyamide yarns, polyacrylonitrile yarns or copolymers containing at least 55% polyacrylonitrile, cellulose acetate yarns, protein yarns, polyvinylchloride yarns, polyethylene yarns, polypropylene yarns, and the like.

Additional novel effects may be produced by extruding a thick and thin yarn composed of variable denier filaments as the stress-bearing element in FIGURES 4 and 5 to be combined with the slub yarn of this invention at the convergence guide.

The primary advantage of the invention lies in the distinctive fabric efiects resulting from the use of the yarn. A further advantage is that the yarn of the invention is composed of individual continuous filaments of uniform or non-uniform filament denier and is produced by a process requiring only slight modification of the ordinary spinning arrangement. Yet, the yarn is characterized by slubs of twisted-in loops at intervals along its length. This type of slub is usually associated only with staple yarns produced on expensive novelty yarn twisters.

The fabrics produced from these yarns are characterized by low cost and novel decorative appearance. They 1'. 1.. may be used for upholstery, bedspreads, robes, rugs, carpets, draperies, lamp shades and wearing apparel.

Many modifications will be apparent to those skilled in the art from a reading of the above without a departure from the inventive concept.

This application is a division of United States application Serial No. 731,954 which in turn is a continuationin-part of United States applications Serial Nos. 555,126 and 555,127 both filed December 23, 1955.

What is claimed is:

1. In a process for producing continuous filament yarn by extruding filament-forming solution through spinneret orifices and into a coagulating liquid flowing through a tube to form separated filaments, flowing the coagulating liquid through the tube at sufficient liquid velocity to transport the filaments through the tube and completing coagulation of the filaments during passage through the tube to form filaments which do not stick together, converging the non-adherent coagulated filaments from the tube within a bath to form a yarn and withdrawing the yarn from the bath, the improvement of intermittently bulking the yarn to form bunches of non-adhered, entangled filaments which comprises discharging the nonadherent coagulated filaments into said bath, from said tube, directly against a baffie to bulk the yarn and withdrawing the yarn from the bath at a rate providing a ratio of yarn speed to said liquid velocity of between 0.50 and 1.30, said ratio being 15% to 50% less than the corresponding ratio when the yarn is withdrawn from the bath without bulking against the baffle, to form tight bunches of at least 2.5 times the denier of the unbulked yarn and of a length from A3 inch to 4 inches spaced at intervals between bunches of 0.5 inch to 20 inches, said bunches consisting of non-adhered filaments which are individually looped upon themselves and upon each other at intervals along their lengths into an entangled mass of ring-like loops, whorls and coils that are not readily pulled apart.

2. The process of claim 1 wherein the filament-forming solution is fed evenly through the spinneret orifices to form constant denier filaments.

3. The process of claim 1 wherein the filament-forming solution is pulsated through the spinneret orifices to form variable denier filaments.

4. The process of claim 1 wherein a second group of filaments is led into the tube to form a slub yarn composed of a blend of difieren-t filaments.

5. A process as defined in claim 1 wherein the ratio of the draw-off speed from the bath to the velocity of coagulating liquid through the tube is between 0.75 and 1.30.

6. The process of claim 1 wherein the yarn is withdrawn from the coagulating bath at a rate of at least about 40 yards per minute.

7. The process of claim 1 wherein said liquid velocity is at least about 47 yards per minute.

References Cited in the file of this patent UNITED STATES PATENTS 2,079,524 Picard May 4, 1937 2,125,230 Hofiman July 26, 1938 2,272,666 Hoffman Feb. 10, 1942 2,337,664 Keight Dec. 28, 1943 2,399,258 Taylor Apr. 30, 1946 2,550,808 Hays May 1, 1951 2,789,315 Pistor Apr. 28, 1957 2,874,445 Gl'iset Feb. 24, 1959 

1. IN A PROCESS FOR PRODUCING CONTINUOUS FILAMENT YARN BY EXTRUDING FILAMENT-FORMING SOLUTION THROUGH SPINNERET ORIFICES AND INTO A COAGULATING LIQUID FLOWING THROUGH A TUBE TO FORM SEPARATED FILAMENTS, FLOWING THE COAGULATING LIQUID THROUGH THE TUBE AT SUFFICIENT LIQUID VELOCITY TO TRANSPORT THE FILAMENTS THROUGH THE TUBE AND COMPLETING COAGULATION OF THE FILAMENTS DURING PASSAGE THROUGH THE TUBE TO FORM FILAMENTS WHICH DO NOT STICK TOGETHER, CONVERGING THE NON-ADHERENT COAGULATED FILAMENTS FROM THE TUBE WITHIN A BATH TO FORM A YARN AND WITHDRAWING THE YARN FROM THE BATH, THE IMPROVEMENT OF INTERMITTENTLY BULKING THE YARN TO FORM BUNCHES OF NON-ADHERED, ENTANGLED FILAMENTS WHICH COMPRISES DISCHARGING THE NONADHERENT COAGULATED FILAMENTS INTO SAID BATH, FROM SAID TUBE, DIRECTLY AGAINST A BAFFLE TO BULK THE YARN AND WITHDRAWING THE YARN FROM THE BATH AT A RATE PROVIDING A RATIO OF YARN SPEED TO SAID LIQUID VELOCITY OF BETWEEN 0.50 AND 1.30, SAID RATIO BEING 15% TO 50% LESS THAN THE CORRESPONDING RATIO WHEN THE YARN IS WITHDRAWN FROM THE BATH WITHOUT BULKING AGAINST THE BAFFLE, TO FORM TIGHT BUNCHES OF AT LEAST 2.5 TIMES THE DENIER OF THE UNBULKED YARN AND OF A LENGTH FROM 1/8 INCH TO 4 INCHES SPACED AT INTERVALS BETWEEN BUNCHES OF 0.5 INCH TO 20 INCHES, SAID BUNCHES CONSISTING OF NON-ADHERED FILAMENTS WHICH ARE INDIVIDUALLY LOOPED UPON THEMSELVES AND UPON EACH OTHER AT INTERVALS ALONG THEIR LENGTHS INTO AN ENTANGLED MASS OF RING-LIKE LOOPS, WHORLS AND COILS THAT ARE NOT READILY PULLED APART. 